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TECHNICAL LIBRARY

Expert: Recent Improvements in Hierarchical Layout Inspection

The functionality of several features of Expert
layout editor enhanced to deal with hierarchical layouts in more convenient
ways.

1. Edit in Place

The Hierarchy>>EIP>>Direct Pick command allows you to
pick an object for editing in place anywhere in cell hierarchy. To facilitate
the choosing of the required object, preselection highlighting is used.

The hierarchy depth at which an object can be picked
is naturally defined by the viewing depth (as defined by commands from
the View>>Cell view submenu). If a primitive object (shape or text) is
picked, then you will edit the cell that contains this object. If a cell
instance/array is picked, then you will edit in place the cell of this
instance.

2. Pick Layer

The Tools>>Pick Layer command now allows you to pick
the layer (i.e., make this layer active) from a shape anywhere in cell
hierarchy. This tool uses preselection-type highlighting of objects to
be picked. As a by-product, one may use this tool to inspect objects deep
in hierarchy: the message line shows a brief description of the object,
like in the case of an ordinary preselection.

3. Node Probing

The function Verification>>Node Probing of Expert/
ExpertViews is redesigned to trace electrically connected nodes
throughout the hierarchy of a cell, unlike flat-mode operation of previous
versions.

In addition, this feature provides an easy and convenient
way to analyze the results of Connectivity/ Netlist extraction directly
on the original hierarchical design and to make necessary corrections
in the design. This tool makes it possible to search and inspect nodes
listed in the extracted netlist file directly in the original layout.

When the menu command Verification>> Node Probing>>Pick
Node is selected, the cursor assumes the node probing shape. It is necessary
to point and click at the geometric object whose electric connections
or device description are to be traced. As a result, the whole net electrically
connected to the probed object or device shape will be highlighted (Figure
1), and you may inspect it using other commands from Verification>>Node
Probing submenu. The corresponding commands can also be executed from
the Node Probing bar. (This bar may be turned on/off by View>>Control
Bars command.)

Figure 1. Electrical node highlighted.

To facilitate the picking of the required object in the
layout, preselection highlighting is used. In addition, it is often convenient
to hide some layers for better selectivity. For example, one may show
only device definition layers to pick from. After an object is picked,
the node probing function ignores layer visibility.

Verification>>Node Probing>>Object Descriptors menu command
shows the Connectivity/Netlist Description Tag that covers the last probed
node and contains information about Net/Device and the origin of the current
shape in the original design (Figure 2).

Figure 2. Object Descriptor for shape in probed node .

There are commands to highlight the consecutive shapes
of the node such as First Object, Previous Object, Next Object, Last Object
They are useful for consecutive node browsing.

For a more detailed inspection, there are such functions
as Zoom to Node (Figure 3), View in Place (Figure 4) and View in Cell
(Figure 7).

Figure 3. Zoom to Node.

Figure 4. View in Place.

It is possible to save the highlighted node into a new
cell for later inspection or for historic references (Figure 5). The command
Verification>>Node Probing>>Copy Node to New Cell copies all geometry
in flat form to a newly created cell.

Figure 5. Copy Node to New Cell

One more function Verification>>Node Search is added
into menu and duplicated in the Search Net/Device Bar, used for searching
the nets or devices by their name. There is an edit field on the Search
Net/Device Bar for typing the name of the net/device to be found and highlighted
in response to Find Device command (Figure 6). The full Spice statement
for the found device will be shown in the Edit Net/Device Name field.

Figure 6. Find Device by Name

Another important function mentioned above is viewing
the highlighted object in the cell where this objected is allocated in
design hierarchy. The result of this operation for a device shown in Figure
6 is represented in Figure 7.